AM 3 tubes (valves) broadcasting regen receiver.

This isn't a specifically designed proyect for ham radio. It's a regenerative 3 tubes I built around 2012/13. It consists on an RF preamplifier in the ECF801 pentode section, grid leak biased wirh 10M and 100pF plate capacitor. It uses 1M screen grid droping resistor bypassed with 1uF Siemens MAC capacitor, like all orange units in the pics. RF signal is captured upon the ferrite rod and coil, the double section brass gang tunes the antenna and the grid of the detector. As inductances are equal, no tracking problems arises.
The ECF801's triode section is the regen itself. Uses only 25/30V anode voltage, 2.2M//47pF leak detector, grid tuned Armstrong type oscillator (tickler coil on plate, all series feed). A throttle capacitor is located between cold side of tickler coil and a RF choke (in the pics you can see a horizontal ringing coil from TV) and audiofrequency choke, a rewound transistor radio transformer, around 8Hy apx.
Both sections of ECL85 tube amps the audiofrequency revovered signal. Smaller iron transformer outside the PCB is the audio output, rewound vertical output from TV too. It has a tap apx at 1/3 of the primary for screen grid of ECL85 pentode (ultralinear connected). There is also a NFB loop from ECL85 pentode to triode's cathode. The +B for this stage is around 160V, the ECL85 has limited the plate voltage to 180/200V.

Biggest transformer, is the power unit. It gives 6.3V for heaters, 140V apx for +B and rectified full wave with 6X4 double diode. 3 units 3.3uF 250V are the input filtering, a choke inductance located under the antenna, 100uF Nichicon unit completes filtering. There is a dropping resistor and other 100uF unit to filter the ripple for detector, very sensible for +B bus ripple.

ECL85 Pentode has a 180R cathode bias with 1000uF Nichicon across it. The dial is one recovered from who knows where.

I use it every day to listen news prior to wake up.
Two small cabinets loated at each side of the bed are the final load.

A smaller independent PCB is a line filter using industrial Siemens coils and Siemens Mac capacitors for reducing line QRM.

The chassis was specifically designed for it in brass thinker, as the two fiber glass PCB's hand routed with unerasable pen. The volume pot is a 2M unit from very old TV's.
Its sensitivity isn't something extraordinary, sufficient to listen local AM radiostations. As any regen, there isn't any converter, mixer or IF section, a single triode with controllable positive feedback (throttle capacitor) does all the job. The pentode unit, among a small amplification, gives isolation from detector to antenna to prevent re-radiation, and making the antenna almost un-sensible to touch it with a hand.

The black coil in front of the ECF801 is the regeneration detector tuned circuit. It is made from scrap of horizontal width coil of videogame monitor.

This is the schematic, made in "ASCII ART" (you can believe me or not, I am still using AMD486 machines @120MHz running pure DOS7.10, and I have 4 of them alive and with CRT screens). Over it, it isn't difficult to understand.


Pics captured directly from CRT screen.

Enjoy!